Method of forming a pillar lantern ring for a shaft sealing system

ABSTRACT

A fluid sealing system for a rotary mechanical device including a pillar lantern ring having a bottom and a top end cap with pillars or columns connecting the end caps is formed by additive manufacturing. The bottom annular end cap has an outside face and an opposed inside face defining a height therebetween and the upper annular end cap has an inside face and an opposed outside face defining a height therebetween with a plurality of integrally formed substantially cylindrical axial columns connecting the two opposed inside faces of the two end caps.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of and is based upon andclaims the benefit of the filing date of co-pending, commonly owned U.S.patent application Ser. No. 16/144,329, filed Sep. 27, 2018, which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to a lantern ring for a shaft sealing system fora mechanical device having a shaft passing through a stuffing box, andmore particularly to the method of manufacture of a lantern ring thathas a pillar or columnar structure between the end caps of the lanternring to provide an increased flush reservoir in the stuffing box.

BACKGROUND OF THE INVENTION

Rotary mechanical devices, such as mixers and centrifugal pumps, includean impeller mounted on a shaft that is driven by a power source, such asan electric motor. The shaft passes through the seal cavity or stuffingbox defined by a cylindrical cavity in the device housing. The shaft issupported by bearings at the motor end of the device. Seals are placedin the stuffing box to prevent process fluid from passing through theseal cavity and reaching the bearing and the motor, potentially causingdamage to both.

In mechanical pumps, the seal cavity restricts passage of chemicalfluids or solvents being pumped, many of which are corrosive.Accordingly, it is important that appropriate packing material is placedwithin the seal cavity. A seal fluid, such as water, is pumped into theseal cavity through a flush port to prevent the fluid being pumped ormixed from travelling along the shaft to the bearings and motor and toprovide lubricant to the rotating shaft. Over extended use, the pumpshaft may develop a whip as the bearings wear. IN view of this, it maybe desirable to provide a sealing system including a bearing to reducewhip that can occur as the shaft rotates, and a lantern ring thatprovides for increased flush to form an effective seal to limit theamount of product from entering the seal cavity.

There are a wide variety of shaft sealing systems available. One suchcommercially successful device is described and claimed in Wilkinson,U.S. Pat. No. 6,834,862 for SHAFT SEALING SYSTEM FOR A ROTARY MECHANICALDEVICE, issued on Dec. 28, 2004. Here, a bearing with an integrallantern ring provides shaft support, and the lantern ring portion allowsfor addition of flush fluid to the seal cavity. Such bearing elementsare custom made for a particular application.

In applications where a separate lantern ring is utilized, one suchsolution was illustrated earlier in Heinz, U.S. Pat. No. 4,498,681 forUNIVERSAL SEAL CAGE LANTERN RING WITH CHANNELS AND FLUID SLOTS, issuedon Feb. 12, 1985. Here, a flexible ring having two ends or lands havingan outer groove and an inner groove with spaced holes through thegrooves for passage of seal fluid from an external port to the rotatingshaft is provided.

These solutions for a standard 2.5 inch bore with a shaft diameter of1.75 inch include cylindrical bearings with an integral lantern ring, orcylindrical bearings or bushings together with an isolated lantern ringstypically have between about six and eight holes formed between theouter surface of the lantern ring groove and the inner surface. Whilethese solutions are highly acceptable for many applications, it isdesirable to provide alternative sealing solutions that provide for anincreased flush reservoir to the stuffing box to protect against astoppage or hiccup in the flow of seal fluid at a reduced cost.

SUMMARY OF THE INVENTION

Generally speaking, in accordance with the invention, an improvedlantern ring having two end caps with pillars or columns between the endcaps of the lantern ring is provided. The pillars or columns are axialsupports to prevent the ring from being crushed when the gland followeris tightened down. The lantern ring is dimensioned to have an outersurface closely dimensioned to the inner bore of the stuffing box. Inone embodiment the lantern ring is a suspended lantern ring with aninner diameter greater than the shaft to avoid any and all contact withthe shaft in order to extend its working life.

The pillar lantern ring is split between two opposite columns or pillarsto provide easy installation over an installed device shaft. There areat least two or three pillars per half so that there at least fourpillars per assembled lantern ring. Preferably, there are at least threeto six pillars per half, and preferably both halves are identical. Thenumber and size of the pillars depends on the overall shaft and stuffingbox dimensions. For large devices a brace or ring is formed between thepillars to provide increased strength and prevent collapse when thegland follower is tightened.

Constructing the lantern ring with pillars having a diameter smallerthan the annular dimension of the lantern ring end caps allows for alarger reservoir volume of flush in case of temporary flush losscompared to a conventional lantern ring with holes between the outer andinner groove surfaces of the lantern ring. In a preferred embodiment ofthe invention, the outer surfaces of one or both of the front and rearend caps may include a groove to receive an O-ring to improve the sealbetween the impeller end and the power end of the stuffing box.

In a shaft sealing system including the pillar suspended lantern ring inaccordance with the invention, a bearing or bushing seal element ispositioned at the impeller end, and at least one complimentary flexiblepacking ring is inserted into the seal cavity at the power end. Usually,three packing rings are preferably installed. The bearing or bushingseal element and the lantern ring are all split to provide easyinstallation over an installed device shaft. The lantern ring inaccordance with the invention having an impeller end cap element and amotor end cap element supported by the pillars is placed at the motorend of the bearing or bushing at the location of the flush port and mayhave an inner diameter greater than the shaft and an outer diameterclosely dimensioned to the inner bore of the stuffing box for extendingthe useful life of the lantern ring.

Accordingly, it is an object of the invention to provide an improvedpillar lantern ring to be inserted into a seal cavity of a rotarymechanical device.

It is another object of the invention to provide an improved pillarlantern ring having columns between a bottom end cap and an upper endcap to be inserted into a seal cavity of a rotary mechanical device.

A further object of the invention is to provide an improved shaftsealing system for a rotary mechanical device including a rigid bearingmember for supporting the impeller end of the device shaft and a pillarlantern ring with an increased reservoir for flush fluid to bepositioned at the flush port.

Yet another object of the invention is to provide an improved shaftsealing system for a rotary mechanical device including a rigid bearingmember and a lantern ring for increasing the amount of seal fluidentering the seal cavity with at least one O-ring positioned on theouter surfaces of the end cap elements of the lantern ring.

Still another object of the invention is to provide an improved pillarlantern ring for a rotary mechanical device having an inner diameterspaced apart from the shaft and an outer diameter closely dimensioned tothe inner bore of the stuffing box with pillars supporting the impellerend cap element and the motor end cap element of the lantern ring toprovide for an increased fluid reservoir in the stuffing box.

Yet another object of the invention is an improved lantern ring with atleast one outer O-ring on each end lantern ring end cap for improvedisolation of the product being handled and seal fluid in the sealcavity.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The invention comprises a product possessing the features, properties,and the relation of components and a method for manufacture which willbe exemplified in the product hereinafter described and the scope of theinvention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the invention, reference is had to thefollowing description taken in connection with the accompanyingdrawings, in which:

FIG. 1 is a partial cross-sectional view of a typical rotary fluid pumpof the type suitable to install a seal system having a pillar lanternring in accordance with the invention;

FIG. 2 is an enlarged cross-sectional view of the seal cavity of thepump of FIG. 1 with a shaft sealing system including a rigid sealelement, a pillar lantern ring and packing in accordance with theinvention;

FIG. 3 is an enlarged cross-sectional view of the seal cavity of thepump of FIG. 1 showing the shaft sealing system of FIG. 2 with an O-ringinstalled on an end cap of the pillar lantern ring in accordance withthe invention;

FIG. 4 is a perspective view of a split pillar lantern ring inaccordance with the invention;

FIG. 5 is a side elevational view of the pillar lantern ring of FIGS. 2and 4;

FIG. 6 is a sectional view of the pillar lantern ring of FIG. 4 takenalong line 6-6 of FIG. 5;

FIG. 7 is a perspective view of the pillar lantern ring of FIG. 4 splitthrough two columns;

FIG. 8 is a perspective view of a pillar lantern ring including oneO-ring on an end cap of the lantern ring;

FIG. 9 is a perspective view of a pillar lantern ring including twoO-rings on the end caps of the lantern ring;

FIG. 10 is a perspective view of a pillar lantern ring including a braceand one O-ring on an end cap of the lantern ring;

FIG. 11 is an elevational view of a pillar lantern ring including abrace and one 0-rings on an end caps of the lantern ring;

FIG. 12 is a perspective view of a pillar lantern ring including a braceand two O-rings on the end caps of the lantern ring;

FIG. 13 is an elevational view of a pillar lantern ring including abrace and two 0-rings on the end caps of the lantern ring; and

FIG. 14 is a perspective view of a pillar lantern ring having end capsof different heights and including a brace and one O-ring on an end capof the lantern ring;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a generic form of a centrifugal pump 11 incross-section mounted on a frame 10. Pump 11 includes a centrifugalimpeller 12 driven by an electric motor 13 that drives a rotary shaft 14coupled to impeller 12. Shaft 14 is supported by a bearing housing 16and rotates to draw fluid in through an impeller inlet 17 and expel thefluid out through a radial impeller outlet 18. Pump 11 includes ahousing 19 that defines a seal cavity or stuffing box 22 and shaft 14passing therethrough as shown in detail in FIG. 2. Housing 19 includesan opening 23 through which shaft 14 passes to engage impeller 12 andalso includes a flush port 25 for introduction of seal fluid, such aswater, into seal cavity 22. Shaft 14 is coupled to impeller 12 by a nutor fastener 24 at the end portion of shaft 14 projecting throughimpeller 12.

Pump 11 operates by drawing a fluid to be pumped into inlet 17. Duringpumping, fluid tends to migrate and be forced into seal cavity 22through opening 23. A wide variety of seals and venting configurationsare available to be placed in seal cavity 22 abutting opening 23 inorder to restrict and limit entry of pumped fluid into seal cavity 22.If fluid enters seal cavity 22 and migrates to bearing housing 16, thebearings will be subject to substantial degradation due to the corrosiveaction of the pumped fluid.

FIG. 2 is an enlarged sectional view of seal cavity 22 with a shaftsealing system in accordance with the invention in place. Seal cavity 22is defined radially by an inner bore 21 and the diameter of shaft 14.The motor end of seal cavity 22 is defined by a gland follower 27mounted on gland bolts 28 and secured in place by gland nuts 29.

As shown in FIG. 2, the shaft sealing system installed in seal cavity 22includes a bearing or bushing seal element 31 positioned against theimpeller end of seal cavity 22 with a pillar lantern ring 30 on themotor side of seal element 31. These elements are secured within sealcavity 22 by at least one compressible packing ring 32 and glandfollower 27. Pillar lantern ring 30 is positioned at the fluid flushport 25. Various types of packing rings suitable for use are shown inU.S. Pat. Nos. 5,370,926, 4,559,862, 4,431,698, 4,371,180 and 4,298,207,the contents of which are incorporated by reference in their entirety.

FIG. 3 is consistent with FIG. 2 and illustrates a shaft sealing systemin accordance with the invention wherein a pillar lantern ring 130includes an O-ring 136 on the power side of lantern ring 130. A bearingor bushing seal element 31 and pillar lantern ring 130 are custom madefor a particular stuffing box of a device and the shaft size.

In FIG. 4, pillar lantern ring 30 is shown in perspective, and in FIG. 5in a side elevational view. Pillar lantern ring 30, as are all theembodiments, is split along a split line 30 a and includes a bottom endcap or land 33 and an upper end cap or land 34 with a plurality ofcolumns 35 therebetween.

As can be seen in FIG. 6, the diameter of each column 35 is smaller thanthe annular radial dimension of end caps 33 and 34. FIG. 6 is asectional view through line 6-6 in FIG. 5 showing. Pillar lantern ring30 includes an even number of columns 35, in this case eight. As can beseen in FIG. 7, when split along split line 30 a, pillar lantern ring 30is split through two opposite columns 35 a to preserve the structuralintegrity of the assembled and installed pillar lantern ring 30. Alsoshown on a face of split column 35 a are a pair of alignment holes 37 inone half and mating alignment pins 38 in a mating half.

In the illustrated embodiment pillar lantern ring 30 includes eightcolumns, but may include anywhere between six and 10 or 12 depending onthe size of the stuffing box and the amount of flush fluid desired toreach the shaft. The more columns present, the lesser the open volumebetween the end caps and less flush.

A perspective view of split pillar lantern ring 30 is shown in FIG. 7.In each case, bottom end cap 33 and top end cap 34 are substantially ofequal length.

As shown in FIG. 8, pillar lantern ring 30 may be formed to include anO-ring 136 in one or both end caps to aid in holding pillar lantern ring30 in place and in sealing. O-ring 136 can be formed of a variety ofresilient materials, including perfluoroelastomers or other resilientmaterial compatible with the pumped fluid for providing an additionalbarrier to isolate the motor end of shaft 14 from fluid entering sealcavity 22. O-ring 136 provides an additional obstacle to prevent fluidfrom entering seal cavity.

FIG. 8 shows pillar lantern ring 130 of FIG. 3 in perspective withO-ring 136. FIG. 9 illustrates a pillar lantern ring 230 with a pair ofO-rings 236 also suitable for use in seal cavity 22 shown in FIGS. 2 and3.

For larger and heavy duty applications and those uses requiring a pillarlantern ring 330 of increased strength, the pillar lantern ring itselfrequires increased strength to prevent it from collapse when the glandfollower is tightened. In this case, a pillar brace 315 shown in FIGS.10 and 11 between pillars 335 imparts additional strength to pillarlantern ring 330 so that it will not collapse when gland follower 27 istightened. Two O-rings may be included on a pillar lantern ring 430 witha brace 415 as shown in FIGS. 12 and 13.

It is fully within the scope of the invention to vary the lengths ofeither or both end caps. In this case FIG. 14 illustrates a sealingelement 530 including a bottom bearing or bushing section 531 formedintegrally with a lantern ring section 532 in an elevational view. Here,upper lantern ring section 532 is formed with a groove 533 for receivingan O-ring 534.

Seal element 31 is a substantially cylindrical rigid member with anouter surface 37 and with an inner bore 38 dimensioned to be slightlylarger than the outer dimension of pump shaft 14 and fit within innerbore 21 of pump housing 19. When formed of bearing grade material andformed with close tolerances, inner bore 38 of seal element 31 providesa bearing surface for shaft 14 when in position as shown in FIGS. 2 and3, and this is custom dimensioned for a particular mechanical device.

Seal element 31 and pillar lantern ring 32 are substantially rigid andformed of materials that will not be attacked or destroyed by corrosivefluids being transported by pump 11. Preferred materials of constructioninclude non-ferrous materials, molybdenum/carbon or glass or carbonfilled thermoplastic material, such as nylon, polytetrafluoroethylene(PTFE), or any other suitable plastic material that will not be degradedby the materials in the device or the temperatures encountered.Materials are selected that can provide a suitable bearing surface andare resistant to most industrial solutions.

Materials are selected that can provide a suitable bearing surface andare resistant to most industrial solutions. Suitable bearing materialsare those that provide suitable chemical, temperature, compressivestrength, flexural strength and wear characteristics and can beappropriately machined to yield the desired bearing dimensions andtolerances. Such bearing materials include, but are not limited to,polymers, including polyphenylene sulfides, polyimidizoles,polyamideimides, polybenzylimidizoles, PEEK polymers obtained bystep-growth polymerization by the dialkylation of bisphenolate salts,PTFE, perfluoroalkoxy, and formulations containing these polymers in amajor proportion.

The pillar lantern ring in accordance with the invention may bemanufactured by machining a hollow cylinder of suitable material,molding, or by additive manufacturing techniques. Preferably, the pillarlantern ring is manufactured by additive manufacturing. These lattertechniques include 3D Printing, Rapid Prototyping (RP), Direct DigitalManufacturing (DDM), layered manufacturing and additive fabrication. Inthis process, 3D objects are built by adding layer-upon-layer ofmaterial, whether plastic, neat or filled, and metal.

In order to install seal element 31 and pillar lantern ring 30 inposition in seal cavity 22, seal element 31 and pillar lantern ring 30are split along a center line 31 a and 30 a, respectively. Splittingseal element 31 and pillar lantern ring 30 allows seal element 31 andpillar lantern ring 30 to be placed about installed shaft 14 and pushedinto position at the impeller end of seal cavity 22. Generally, at leastone, and preferably three, packing rings 32 are positioned on the glandside of pillar lantern ring 32.

Seal element 31 and pillar lantern ring 30 are split along center lines31 a and 31 b and are formed with a pair of corresponding holes 41 onboth halves of split bushing seal 31 for receiving mounting pins 42 forrealignment and reassembly of seal element 31. In this construction,pins 42 insure that when seal element 31 and pillar lantern ring 30 aresecured about shaft 14, the open volume around pillars 35 are properlyaligned on both sections. The length of pillars 35 are dimensioned toalign with flush port 25 formed in housing 19.

In a conventional lantern ring of the type shown in the Heinz patent orin Wilkinson's integral bearing and lantern ring patent, grooves areformed on both the inner and outer surfaces and holes are made betweenthe grooves to provide fluid access fro the flush port to the shaft.Pillar lantern rings in accordance with the invention in essence providetwo end caps and supporting columns between the end caps. The pillarconstruction provides for a substantial increase in available volume tohold flush fluid.

The following Example is set forth by way of illustration to helpexplain the invention, and is not intended to be limiting in any way.

Example 1

A pillar lantern ring prepared for the stuffing box of a device with a2.50-inch bore and a 1.75-inch diameter shaft typically will have aradial width of 0.375 inch. The overall height is 0.875 inch, and eachend cap is 0.125 inch in height. Each half of the lantern ring has threefull pillars and two halves at each end and has a void volume betweenthe end caps of 0.9876 inch³. In contrast, a combined bearing andlantern rig element constructed pursuant to the Wilkinson patent of thesame dimensions and 8 flush holes between the inner and outer flushgrooves yields a void volume of 0.480 inch³. Thus, a pillar lantern ringprovides more than double the flush fluid to the shaft.

In this Example, columns 35 are 0.25 inch in diameter, and the radialdimension of end caps 33 and 34 is 0.375 inch, or about two-thirds theradial dimension. The diameter may vary from about 50 to 100% of theradial dimension. Increasing the diameter reduces the volume, andreducing the diameter reduces the strength of the pillar lantern ring.

A pillar lantern ring design in accordance with the invention, inaddition to providing a larger sump at pressure, also substantiallyreduces turbulence in that sump by virtue of smooth round, obround, oroval pillars. This eliminates “choke” points and pressure drops presentin conventional lantern rings (holes drilled 90 degrees to the plane ofthe lantern ring web), thus providing instant delivery of fluid from theinlet flush hole to the shaft.

Packing materials are described in the aforementioned U.S. Pat. Nos.4,298,207, 4,371,180, 4,431,698, 4,559,862, and 5,370,926, the contentsof each of which are incorporated herein by reference in their entirety.More particularly, useful materials include, but are not limited to,mechanically and/or thermally resilient component of graphite tape,expanded graphite foil, graphite fiber, carbon fiber, polybenzimidazole(PBI) fiber, PEK fiber, PEEK fiber, PFA fiber, aromatic polyamide fiber,Inconel or Monel wire, or combinations thereof. In another aspect of theinvention, the at least one packing member is a material selected fromthe group consisting of carbonized yarns, graphitized yarns, exfoliatedgraphite yarns, ceramic yarns, and glass yarns. Tension or lip sealrings may comprise the same or different components of the same ordifferent components. The packing rings or members may comprisemechanically and/or thermally components, whether individually or bycombinations thereof, i.e., corner yarns, resilient core, etc. Thedesigns and materials are chosen to resist packing consolidation.

Braided packing rings may include fibers of flax, jute, asbestos, or asynthetic material, such as polytetrafluoroethylene, which fibers areformed into yarns or strands and which are braided together about corestrands. The result is typically a packing having a square cross-sectionand herringbone weave pattern extending in an axial direction along thepacking. Typical packing members are illustrated in U.S. Pat. No.3,646,846, incorporated herein by reference.

It can readily be seen that the seal system including a cylindrical sealand seal system constructed in accordance with the invention can beeasily installed in a conventional rotary impeller pump with pins toguarantee alignment of the seal upon installation. Generally threepacking rings are added to complete installation. When in place, abearing seal element 31 will support the impeller end of pump shaft 14,providing an additional bearing surface to aid in eliminating the whipcommonly found in pump shafts. Since the clearance between pump shaft 14and seal element is relatively small, seal water entering the openvolume in pillar lantern ring 30 would be considerably throttled,thereby minimizing the quantity of seal water flushing and lubricatingthe bearing and finally entering into and diluting the product beingpumped.

Due to the close tolerances available, improved support of the impelleris assured, resulting in longer life of the main bearings and packingmaterials as well as reduced wear of the throat of the rotary device.Minimum seal water is required with less product contamination becauseof this throttling effect. Minimum external leakage also results fromthe installation of the sealing system constructed and arranged inaccordance with the invention.

It will thus be seen that the object set forth above, among those madeapparent from the preceding description are efficiently attained and,since certain changes may be made in the device set forth withoutdeparting from the spirit and scope of the invention, it is intendedthat all matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense. Each split half has a pillar at each end of thesemi-circular part that is split and when installed and mated with asecond half yields a part with a full pillar at he split for providingstructural integrity. Thus, each installed lantern ring will have aneven number of pillars.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed and all statements of the scope of the invention, which, as amatter of language, may be said to fall there between.

What is claimed is:
 1. A method for forming a pillar lantern ring foruse in an annular seal cavity of a rotary mechanical device having anoutput end and a power end with a shaft running through the seal cavity,comprising: using additive manufacturing to form a substantially rigidunitary cylindrical body having an outside surface dimensioned to fitinto the annular seal cavity of the rotary mechanical device with abottom annular end cap having an outside face and an opposed inside facedefining a height therebetween and an upper annular end cap having aninside face and an opposed outside face defining a height therebetweenwith a plurality of integrally formed substantially cylindrical axialcolumns connecting the two opposed inside faces of the two end caps. 2.The method for forming the pillar lantern ring of claim 1, includingforming columns that are cylindrical.
 3. The method for forming thepillar lantern ring of claim 2, including forming columns that have adiameter smaller than the radial thickness of the annular end caps. 4.The method for forming the pillar lantern ring of claim 1, includingforming columns that have fillets at both ends of the columns connectingto the end caps.
 5. The method for forming the pillar lantern ring ofclaim 1, including forming the unitary body with the height of each ofthe two end caps substantially the same.
 6. The method for forming thepillar lantern ring of claim 1, including forming unitary body with theheight of each of the two end caps not substantially the same.
 7. Themethod for forming the pillar lantern ring of claim 1, including formingan even number of columns.
 6. The method for forming the pillar lanternring of claim 1, including forming the substantially rigid cylindricalbody from a non-ferrous metal material.
 7. The method for forming thepillar lantern ring of claim 1, including forming the substantiallyrigid cylindrical body from a thermoplastic material.
 8. The method forforming the pillar lantern ring of claim 7, including forming theunitary body from a thermoplastic material filled with at least one ofcarbon, glass and mixtures thereof.
 9. The method for forming the pillarlantern ring of claim 1, including forming a groove on the outer grooveof at least one of the end caps for receiving an O-ring.
 10. The methodfor forming the pillar lantern ring of claim 9, including forming anO-ring groove on the outer surface of both end caps.
 11. The method forforming the pillar lantern ring of claim 1, including the step ofsplitting the body axially to facilitate installation over an installedshaft.
 12. The method for forming the pillar lantern ring of claim 11,including forming corresponding alignment holes in each of the splithalves.
 13. The method for forming the pillar lantern ring of claim 1,wherein the additive manufacturing is selected from 3D Printing, RapidPrototyping (RP), Direct Digital Manufacturing (DDM), layeredmanufacturing and additive fabrication.
 14. The method for forming thepillar lantern ring of claim 1, wherein the additive manufacturing is 3DPrinting.